Assessment of Regional Ventilation During Recruitment Maneuver by Electrical Impedance Tomography in Dogs

Aline Magalhães Ambrósio; Ana Flávia Sanchez; Marco Aurélio Amador Pereira; Felipe Silveira Rego Monteiro De Andrade; Renata Ramos Rodrigues; Renato de Lima Vitorasso; Henrique Takachi Moriya; Denise Tabacchi Fantoni

doi:10.3389/fvets.2021.815048

Assessment of Regional Ventilation During Recruitment Maneuver by Electrical Impedance Tomography in Dogs

Front Vet Sci. 2022 Feb 14:8:815048. doi: 10.3389/fvets.2021.815048. eCollection 2021.

Authors

Aline Magalhães Ambrósio¹, Ana Flávia Sanchez¹, Marco Aurélio Amador Pereira¹, Felipe Silveira Rego Monteiro De Andrade¹, Renata Ramos Rodrigues¹, Renato de Lima Vitorasso², Henrique Takachi Moriya², Denise Tabacchi Fantoni¹

Affiliations

¹ Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
² Laboratory of Biomedical Engineering, Escola Politecnica, University of São Paulo, São Paulo, Brazil.

Abstract

Background: During protective mechanical ventilation, electrical impedance tomography (EIT) is used to monitor alveolar recruitment maneuvers as well as the distribution of regional ventilation. This technique can infer atelectasis and lung overdistention during mechanical ventilation in anesthetized patients or in the ICU. Changes in lung tissue stretching are evaluated by monitoring the electrical impedance of lung tissue with each respiratory cycle.

Objective: This study aimed to evaluate the distribution of regional ventilation during recruitment maneuvers based on the variables obtained in pulmonary electrical impedance tomography during protective mechanical ventilation, focusing on better lung recruitment associated with less or no overdistention.

Methods: Prospective clinical study using seven adult client-owned healthy dogs, weighing 25 ± 6 kg, undergoing elective ovariohysterectomy or orchiectomy. The animals were anesthetized and ventilated in volume-controlled mode (7 ml.kg^-1) with stepwise PEEP increases from 0 to 20 cmH₂O in steps of 5 cmH₂O every 5 min and then a stepwise decrease. EIT, respiratory mechanics, oxygenation, and hemodynamic variables were recorded for each PEEP step.

Results: The results show that the regional compliance of the dependent lung significantly increased in the PEEP 10 cmH₂O decrease step when compared with baseline (p < 0.027), and for the nondependent lung, there was a decrease in compliance at PEEP 20 cmH₂O (p = 0.039) compared with baseline. A higher level of PEEP was associated with a significant increase in silent space of the nondependent regions from the PEEP 10 cmH₂O increase step (p = 0.048) until the PEEP 15 cmH₂O (0.019) decrease step with the highest values at PEEP 20 cmH₂0 (p = 0.016), returning to baseline values thereafter. Silent space of the dependent regions did not show any significant changes. Drive pressure decreased significantly in the PEEP 10 and 5 cmH₂O decrease steps (p = 0.032) accompanied by increased respiratory static compliance in the same PEEP step (p = 0.035 and 0.018, respectively).

Conclusions: The regional ventilation distribution assessed by EIT showed that the best PEEP value for recruitment maintenance, capable of decreasing areas of pulmonary atelectasis in dependent regions promoting less overinflation in nondependent areas, was from 10 to 5 cmH₂O decreased steps.

Keywords: atelectasis; low tidal volume; overdistention; oxygenation; protective mechanical ventilation; respiratory mechanics; stretch.